OBJECTIVES: Poly ADP-ribosylation of basic chromosomal proteins has been reported to occur both in vivo and in vitro. Functionally, this modification may present a mechanism for disrupting the electrostatic attraction between positively charged basic proteins and negatively charged chromosomal DNA. The reaction is thus likely involved in altering the degree of chromatin condensation during processes such as DNA and RNA synthesis, DNA repair or in preparation for mitosis. The process of poly ADP-ribosylation of chromosomal proteins is most likely a reversible one since poly (ADP-ribose) turns over rapidly via an enzyme, poly(ADP-ribose) glycohydrolase, present in chromatin. The objectives of this project are twofold: (1) to purify and characterize the activity of poly(ADP-ribose) glycohydrolase; and (2) to correlate the differences in the relative amounts of enzyme activity present in normal versus neoplastic tissue. BIBLIOGRAPHIC REFERENCE: Stone, P.R., Lorimer, III, W.S. and Kidwell, W.R. Proceedings of the 4th International Symposium on Poly (ADP-Ribose) and ADP-Ribosylation of Proteins. (Ed., H. Hilf) Walter de Gruyter, Berlin, N.Y., 1976, p.6.